Arc tube



FIG. 1 is a front view of an arc tube of the present invention;

FIG. 2 is a rear view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a top view thereof; and,

FIG. 6 is a bottom view thereof. 

We claim the ornamental design for an arc tube, as shown and described. 